集约化生产对农田土壤碳氮含量及δ^(13)C和δ^(15)N同位素丰度的影响

Effects of intensive agricultural production on farmland soil carbon and nitrogen contents and their δ^(13)C and δ^(15)N isotope abundances

集约化生产下农田土壤碳、氮含量变化是衡量土壤肥力持久性的重要指标.对常规水稻-蚕豆轮作地、露地蔬菜地、3年塑料大棚地和10年以上塑料大棚地的土壤pH、电导率(EC)、土壤有机碳(SOC)和总氮(TN)含量及δ13C和δ15N同位素丰度进行测定,研究了集约化生产程度对土壤特性的影响.结果表明:与水稻-蚕豆轮作地相比,露地蔬菜地、3年塑料大棚地和10年以上塑料大棚地0～20 cm耕层土壤pH分别降低1.1、0.8和0.7,而土壤EC分别是水稻-蚕豆轮作地的4.2、4.9和5.2倍;土壤碳、氮含量随塑料大棚地生产年限的增加总体上呈先增大后减小的趋势.与水稻-蚕豆轮作地相比,10年以上塑料大棚地0～20、20～40、40～60、60～80、80～100 cm土层的土壤SOC含量分别下降了54%、46%、60%、63%和59%,土壤TN含量分别下降了53%、53%、71%、82%和85%.农田集约化生产程度显著影响土壤SOC、TN含量和δ13C、δ15N丰度,土壤δ13C丰度与SOC含量呈显著负相关.土壤δ13C丰度可作为评价农田土壤碳循环受人为干扰强度的指标.

Farmland soil carbon and nitrogen contents under intensive agricultural production are the important indices for the assessment of the soil fertility sustainability.This paper measured the soil pH,electrical conductivity（EC）,organic carbon（SOC）,total nitrogen（TN）,and δ13C and δ15N isotope abundances of four types of farmland,i.e.,conventional rice-broad bean rotation field,open vegetable field,3-year plastic covered greenhouse field,and 10-year plastic covered greenhouse field,aimed to understand the effects of intensive agricultural production degree on soil properties.In the open vegetable field,3-year plastic covered greenhouse field,and 10-year plastic covered greenhouse field,the soil（0-20 cm） pH decreased by 1.1,0.8,and 0.7,and the soil EC was 4.2,4.9,and 5.2 folds of that in conventional rice-broad bean rotation field,respectively.With the increasing year of plastic covered greenhouse production,the soil SOC and TN contents decreased after an initial increase.Comparing with those under rice-broad bean rotation,the SOC content in 0-20,20-40,40-60,60-80 and 80-100 cm soil layers in 10-year plastic covered greenhouse decreased by 54%,46%,60%,63%,and 59%,and the TN content decreased by 53%,53%,71%,82%,and 85%,respectively.Intensive agricultural production degree had significant effects on the soil SOC and TN contents and δ13C and δ15N abundances.The δ13C abundance was significantly negatively correlated with the soil SOC,suggesting that the soil δ13C abundance could be regarded as an index for the assessment of carbon cycle in farmland soils under effects of human activities.